feat(web): restyle Artists, Discover, Wanted, discography + preview (Phase 2)

Convert the remaining pages onto the Pressing Plant system: PageHead
component, shared list-row / toggle / small+ghost button / tracklist classes,
and page wrappers trimmed now that the shell provides masthead + nav. All
logic and test hooks (aria-labels, button text) preserved. Verified in the
real app across both themes (Playwright): artists/discover/wanted/discography
render cohesively with real data.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web/src/app/discover/page.tsx

@@ -1,14 +1,5 @@
 import { DiscoverClient } from "./discover-client";
 
 export default function DiscoverPage() {
-  return (
-    <main>
-      <h1>Discover</h1>
-      <p>
-        <a href="/">Home</a> · <a href="/artists">Artists</a> · <a href="/wanted">Wanted</a> ·{" "}
-        <a href="/settings">Settings</a>
-      </p>
-      <DiscoverClient />
-    </main>
-  );
+  return <DiscoverClient />;
 }